Wheel bearing devices for automobiles generally are due of two types: One for driving wheels and the other for non-driving wheels. In wheel bearing devices, the planar runout of the braking surface occurring during the rotation of the brake rotor causes brake judder during the brake application, and hence high cutting accuracy and high dimensional accuracy are required in the individual parts of the wheel bearing device. Even if the cutting accuracy in individual parts is enhanced, however, not only do the cutting errors in the individual parts accumulate during the assembling of the wheel bearing device, but also assembling errors occur, so that the planar runout of the braking surface of the brake rotor cannot be suppressed.
To eliminate such drawbacks, there have already been proposed methods for cutting the braking surface, the methods comprising mounting on a cutting machine a brake rotor-equipped wheel bearing device assembled in its mounted state and rotating the brake rotor with the brake rotor-equipped wheel bearing device supported in its mounted state (Japanese Unexamined Patent Publication H11-19803, Japanese Unexamined Patent Publication 2000-356233, and U.S. Pat. Nos. 6,158,124 and 6,247,219.
According to the cutting methods, since the braking surface of the brake rotor is cut with the brake rotor-equipped wheel bearing device held in its mounted state, accumulative errors in the form of accumulative cutting errors in the individual parts, and strains produced during the fixing of the brake rotor are eliminated by cutting. Consequently, assembling the brake rotor-equipped wheel bearing device having undergone cutting, to an actual car results in the brake rotor-equipped wheel bearing device being restored to its state of having undergone cutting, the planar runout of the braking surface occurring during the rotation of the brake rotor being very little, enabling the brake rotor to rotate with extremely high accuracy.
Conventional cutting methods for cutting the braking surface of the brake rotor with a brake rotor-equipped wheel bearing device held in its mounted state are cutting methods which are intended to suppress the planar runout of the braking surface occurring during the rotation of the brake rotor and to prevent vibrations from occurring during the brake application, and which are so arranged that, of inner and outer members relatively rotating through rolling bodies, the inner member is fixed, in which state the braking surface of the brake rotor assembled to the inner member is cut; thus, the rolling body contact surfaces are deformed during the cutting load application, which deformation causes deflections in the bearing rotation axis and cutting axis, resulting in the planar runout accuracy being degraded by an amount corresponding to the deflections.